Phenotyping of Idiopathic Calcium Oxalate Stone Formers Reveals Risk Factors for Papillary Lesions and Chronic Renal Function

Abstract

Background:

Idiopathic calcium oxalate stone formers (ICSFs) are a heterogeneous group. Randall’s plaque (RP) and ductal plugs are two common papillary features observed in ICSFs. These papillary phenotypes, implicated in early stone formation, may be susceptible to different risk factors and have differing long-term health outcomes such as stone events and kidney function. We investigate these outcomes using clinical data from a well-characterized cohort of ICSFs undergoing endoscopic stone removal.

Methods:

ICSFs undergoing stone removal procedures were consented for the study between August 2005 and May 2023. Papillae were imaged endoscopically per standard protocol. Two 24-hour urine tests were collected postoperatively while patients were off stone prevention medications. Chart review was performed for comorbidities, serum laboratories, and medication usage related to stone formation.

Results:

We identify three distinct phenotypes. Of 106 ICSFs, 37 had high plugging without plaque, 44 had high plaque without plugging, and 25 had low plaque and low plugging. High plugging ICSFs had lower estimated glomerular filtration rate (eGFR), increased history of prior urinary tract infection (UTI), and more prior stone events than ICSFs with high plaque or neither feature. Multivariable regression revealed plugging as a significant predictor of eGFR when correcting for age, gender, prior UTIs, and prior stone events.

Conclusions:

Plugging appears to be an important predictor for eGFR and multiple stone events. Prior UTIs appear to have a significant effect on plugging. RP did not appear to influence stone events or kidney function.